A key to understanding the origin and maintenance of the diversity of life is to understand how phenotypic and genetic variation is partitioned within and among populations. I characterize the spatial partitioning of phenotypic and genetic variation in an old Willamette Basin freshwater distribution of threespine stickleback (Gasterosteus aculeatus) and compare these results to younger populations. Phenotypic variation was measured using 14 phenotypic traits, and genetic variation was assessed using RADseq and Stacks software to identify tens of thousands of single nucleotide polymorphisms. The major partitioning of phenotypic and genetic variation in Oregon is along a stereotypical transition from oceanic to freshwater that has been seen in younger systems. Phenotypic and genetic variation is significantly partitioned between basin populations, and the genetic variation is geographically structured. This work suggests that parallel divergence between oceanic and freshwater forms originated before the end of the last glacial maximum.

A population of threespine sticklebacks (Gasterosteus aculeatus) infected with the cestode parasite S. solidus was studied to determine the effects of the parasite on stickleback reproductive. success, mortality rates, and swimming ability. The S. solidus infection increased stickleback mortality rates in 'natural' mortality, and in stressed mortality (low oxygen, high temperature) experiments. Infections of S. solidus at intensities of 30% of the stickleback body weight or greater, clearly affect the sticklebacks ability to swim. How infections at this or lesser levels effect predation on parasitized sticklebacks was not established. The effects of S. solidus on stickleback reproductive success were found to be minimal in this study, chiefly because the stickleback breeding season is essentially complete before the S. solidus infection becomes severe. / Science, Faculty of / Zoology, Department of / Graduate

Two morphologically and ecologically distinct forms of threespine stickleback (Gasterosteus), a "limnetic" form and a "benthic" form, co-exist in Enos Lake on Vancouver Island. I used three experiments to compare the feeding performance of the two forms, to test the hypothesis that limnetics are adapted to planktivory and benthics are adapted to foraging on benthic substrates. The results support this conclusion. When tested for maximum prey size, benthics were able to consume larger prey (relative to their body size) than limnetics. Benthics were also more successful than limnetics in foraging on a benthic substrate. When allowed to forage on a detritus substrate for a fixed time interval, benthics of both sexes captured more prey than male limnetics, despite the fact that male limnetics directed as many feeding strikes at the substrate as did the benthics. Female limnetics did not forage on the substrate at all. In contrast, limnetics were more successful in feeding on plankton than benthics. When held in mesh enclosures suspended in the water column of Enos Lake, limnetics consumed more plankton than benthics. "Small" limnetics (26-35 mm standard length) consumed nearly four times more plankton than "large" limnetics (44-50 mm standard length). The small limnetics were all either mature females or immature males; the large limnetics were all mature males. These results, along with morphological, biochemical, ecological and behavioural data obtained in other studies, support the conclusion that the two forms of Gasterosteus in Enos Lake are distinct biological species. The results of this study also support another (unexpected) conclusion: mature male and female limnetics also differ in feeding behaviour. Female limnetics appear to be almost totally planktivorous; whereas, male limnetics are intermediate between female limnetics and benthics (both sexes) in feeding behaviour. / Science, Faculty of / Zoology, Department of / Graduate

Two small streams on Vancouver Island, British Columbia, were examined for patterns of morphological variation in Gasterosteus aculeatus. A progressive analysis beginning with Principle Components Analysis, followed by Nested and Partially Nested Multiple Analysis of Variance and then Duncan's Multiple Range Test was used for pattern determination. This new technique allows the researcher to sequentially isolate the pattern of variation at different levels of generality from species to individual organisms. The pattern of variation for G. aculeatus in Bonsall Creek and Nunns Creek can be summarized as follows: The largest amount of variation accounted for by the analysis is interpreted as individual variation. Populations also account for a large amount of variation and show consistent, fully nested patterns of variation at each of the analysed geographic and microgeographic levels. These populations are probably genealogical units. The so-called "leiurus" and "trachurus" forms on the Pacific coast of North America do not appear to be evolutionary entities, but to be historical artifacts that are best viewed as labels for the extremes of a continuum of variation. In areas where distinct populations meet, different clines are documented in the two stream systems. In Nunns Creek there is a smooth cline between populations, whereas in Bonsall Creek there is a step cline. / Science, Faculty of / Zoology, Department of / Graduate

Commercial fishing in the Baltic Sea has led to decrease in abundance of large predatory fish and as a result the predation pressure on smaller fish species has been reduced. Three-spined stickleback (Gasterosteus aculeatus) is among the species that have benefited from reduced predation pressure. Sticklebacks are a small fish species that spends its juvenile stage in coastal habitat and its adult stage in the open sea with a yearly migration from the sea to coastal habitat and lakes for spawning. Sticklebacks have been shown to have a negative effect on fry of coastal species, such as perch (Perca fluviatilis). Therefore an increase in stickleback abundance, as a consequence of reduced predation pressure, can potentially further reduce abundance of fry of coastal species, such as perch. On the other hand sticklebacks could be subject to predation from adult perch. This two-species interaction is studied in the perspective of general ecological IGP (intra guild predation) theory. In order to determine how the observed increase of three-spined sticklebacks negatively or positively affects the growth of different stages of perch, a time series of operculum bones from perch collected by the coastal monitoring program prior to the increase of sticklebacks and up until present was analyzed. Three areas along the Swedish coast showing increased stickleback abundance (Gaviksfjärden, Norrbyn and Holmön) were compared to areas that had no sticklebacks or only a small increase in abundance (Kinnbäcksfjärden, Råneåfjärden, Långvindsfjärden) prior and after the general increase in stickleback density. In addition to the growth analysis, a dietary analysis of perch was carried out in order to determine to what extent perch utilize sticklebacks as a food source. I found that there were significant differences in regard to perch growth between the two time periods; however there was no significant difference in growth between the control areas and the stickleback areas except for perch of medium size. Further, this difference in growth between the control and stickleback areas was present both before and after the stickleback increase and could therefore not be tied directly to stickleback increase. Consequently, results from a multiple regression showed that stickleback abundance was not able to significantly explain the observed changes in perch growth. The dietary analysis showed that larger and intermediate perch tend to consume sticklebacks as well as benthic fauna and other fish species while smaller perch tended to feed exclusively on smaller invertebrates. This study concluded that the increase in stickleback abundance had only a very weak effect on perch growth.

For the past few years there has been increasing concern surrounding a group of chemicals known as phthalate esters. In mammals, phthalates are known antiandrogens, interfering with the production or activity of testosterone. Phthalates are ubiquitous in the aquatic environment. With recent findings suggesting that antiandrogens may be responsible for much of the endocrine disruption found in wild fish populations, the study of phthalate esters has become integral to determining whether or not these anti-androgenic chemicals are of concern. I investigated whether di-n-butyl phthalate (DBP) was able to cause antiandrogenic endocrine disruption in fish under controlled laboratory conditions. Three experiments were undertaken. In the first study, two generations of fathead minnows were exposed to nominal concentrations of 6 to 100 μg/L for 21 and 150 days, respectively. The second experiment examined the effects of early life-stage exposure to DBP (50, 100 and 200 μg DBP/L) on three-spined sticklebacks. The final experiment examined the effects of DBP on adult male three-spined sticklebacks in a 21-day nesting study (15 and 35 μg DBP/L). DBP had no effect on the fecundity, survival, growth, sex ratio, or gonadal histology of the exposed fish in any of the experiments. Further, it failed to alter the expression of two steroidogenic genes in adult male sticklebacks. In contrast, DBP was often found to significantly alter plasma androgen concentrations in both species, and spiggin concentrations in the three-spined stickleback, most notably causing significantly reduced spiggin concentrations in the adult males exposed to DBP. Ultimately, DBP-exposure did not disrupt the ability of the fish to reproduce successfully, and did not appear to alter reproductive behaviours or the expression of secondary sexual characteristics. In conclusion, while DBP did appear to have some capacity for endocrine disruption in fish, it was unable to interfere with the ability of the fish to develop normally and reproduce successfully. Thus, environmentallyrelevant concentrations of phthalate esters are likely not of particular concern to fish populations.

Coastal populations of perch (Perca fluviatilis) in the Baltic Sea has declined substantially the last decades while the populations of three-spined sticklebacks (Gasterosteus aculeatus) has increased rapidly during the same time period. Earlier studies have suggested that predation on perch larvae and or competition from sticklebacks are the causes behind the decline in perch. To test if predation from sticklebacks commonly occur on perch larvae as well as provide data on stickleback diets in general, diets of sticklebacks were examined by looking at the stomach content of collected samples of sticklebacks from different bays along the Swedish and Finnish coast. Results showed no evidence of stickleback predation on perch larvae as no perch larvae were found in any of the examined stomachs.  Three-spined sticklebacks generally had the same diet in all studied bays consisting mainly of Chironomidae and Asellus aquaticus. The diet results suggest that competition between perch larvae and sticklebacks is minor if any due to low proportions of zooplankton found in the stomachs of the sticklebacks while zooplankton is the main food source for perch larvae. In bays where three spined sticklebacks were found with nine-spined sticklebacks they generally had similar diets. Still, due to a larger size and gape size of three-spined sticklebacks they fed more on larger prey like Asellus aquaticus while nine-spined sticklebacks contained smaller prey such as benthic cladocerans. Due to few samples from bays where sticklebacks were found together with perch larvae, no conclusion regarding predation on larvae as the main the mechanism for declines in coastal perch population can be drawn from the results in this study.

<p>This study used amplified fragment length polymorphism (AFLP) to detect changes of genetic variation in threespine stickleback exposed to industrial pollution from pulp- and paper mills along the southern east coast of Sweden. A general loss of allelic diversity was associated with exposure (table 3, linear model, F1,4=7.2 [P=0.055]) and exposed populations also displayed a similar pattern of response (fig 5) despite geographic distance, indicating that evolution toward pollution resistant ecotypes of threespine stickleback is occurring in the Baltic Sea. The result suggests that pollution can be regarded as an agent of directional selection, causing a decrease of evolutionary potential of exposed species in the Baltic Sea.</p>

This study used amplified fragment length polymorphism (AFLP) to detect changes of genetic variation in threespine stickleback exposed to industrial pollution from pulp- and paper mills along the southern east coast of Sweden. A general loss of allelic diversity was associated with exposure (table 3, linear model, F1,4=7.2 [P=0.055]) and exposed populations also displayed a similar pattern of response (fig 5) despite geographic distance, indicating that evolution toward pollution resistant ecotypes of threespine stickleback is occurring in the Baltic Sea. The result suggests that pollution can be regarded as an agent of directional selection, causing a decrease of evolutionary potential of exposed species in the Baltic Sea.

Climate change is a global issue and the effects on fish populations remain largely unknown. It is thought that climate change could affect fish at all levels of biological organisation, from cellular, individual, population and community. This thesis has taken a holistic approach to examine the ways in which climate change could affect fish from both tropical, marine ecosystems (Great Barrier Reef, Australia) and temperate, freshwater ecosystems (non-tidal River Thames, Britain). Aerobic scope of coral reef fish tested on the Great Barrier Reef was significantly reduced by just a 2°C rise in water temperature (31, 32 and 33°C, compared to the current summer mean of 29°C) due to increased resting oxygen consumption and an inability to increase the maximal oxygen uptake. A 0.3 unit decline in pH, representative of ocean acidification, caused the same percentage loss in aerobic scope as did a 3°C warming. Interfamilial differences in ability to cope aerobically with warming waters will likely lead to changes in the community structure on coral reefs with damselfish replacing cardinalfish. Concerning Britain, there is evidence of gradual warming and increased rainfall in winter months over a 150 year period, suggesting that British fish are already experiencing climate change. It was evident from an analysis of a 15 year dataset on fish populations in the River Thames, that cyprinid species displayed a different pattern in biomass and density to all the non-cyprinid fish population, suggesting that there will be interfamilial differences in responses to climate change. Using a Biological Indicator Approach on the three-spined stickleback, Gasterosteus aculeatus, a 2°C rise in water temperature resulted in a stress response at the cellular and whole organism level. A 6°C rise in temperature resulted in a stress response at the biochemical level (higher cortisol and glucose concentrations), cellular level (higher neutrophil: lymphocyte ratio) and whole organism level (higher ventilation rate and lowered condition factor, hepatosomatic index and growth). G. aculeatus is considered to be temperature tolerant; therefore these results indicate that climate change may prove to be stressful for more temperature-sensitive species. This study has demonstrated that climate change will have direct effects on fish populations, whether they are in temperate regions such as Britain or in tropical coral reefs, but with strong interfamilial differences in those responses.